Tunable high frequency electric discharge device with internal resonator



Feb. 22, 1966 J BEGGS TUNABLE HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE WITH INTERNAL REsoNAToR Filed Nov 21, 1962 /nvem0r James E. Beggs,

H/s Azzomey.

United States Patent Ofiice 3,237,049 Patented Feb. 22, 1966 TUNABLE HIGH FREQUENCY ELECTRIC DISCHARGE DEVICE WITH INTERNAL RESONATOR James E. Beggs, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed Nov. 21, 1962, Ser. No. 239,113 2 Claims. (Cl. 31539) The present invention relates to an improved electric discharge device and more particularly to such a device having a built-in tunable output resonator.

At hi her frequencies of operation the size of the electric discharge devices tend to become smaller and the associated electric circuits also tend to become smaller. Accordingly, it may be desirable to incorporate the circuit directly in the structure forming the electric discharge devices. There have been prior art attempts to incorporate the circuit into the electric discharge device structure in varying degrees but these have not been entirely satisfactory and the present invention is directed particularly to an improved structure providing an internal output cavity, i.e., a cavity provided directly by the electron tube structure which, in the preferred form, is tunable or adjustable and is provided with an improved radial output for transmitting high frequency electrical energy to an associated waveguide.

The features and advantages which characterize my invention will become more apparent as the following description proceeds, reference being had to the accompanying drawing and its scope will be pointed out in the appended claims. In the drawing:

FIG. 1 is an elevational view in section of an electric discharge device embodying my invention; and

FIG. 2 is a sectional view taken along line 22 of FIG. 1.

In the preferred embodiment illustrated the envelope of the device is made up of generally circular or annular metal and insulating members alternately arranged and bonded together to provide the hermetically sealed envelope. As illustrated the device includes a circular disk heater terminal 10, an annular cathode terminal 11, an annular grid terminal 12, and an anode terminal 13. Annular insulating disks, preferably in the form of ceramic disks of either alumina or in the preferred embodiment illustrated, a titanium expansion matching ceramic of forsterite. The annular member 15 .is interposed between the heater terminal and cathode terminal 11, the annular member 16 is interposed between cathode terminal 11, the grid terminal 12, and annular insulator 17 is interposed between grid terminal 12 and a disk-like flexible diaphragm member 18 which is bonded to the anode terminal 13 and forms the hermetic end closure of the device. The insulator 17 not only provides a part of the envelope wall and the direct current insulation between the grid terminal 12 and the anode 13, but also provides the dielectric spacer between these conducting members which provide a radial waveguide or transmission line for conducting electromagnetic energy from the device to an external circuit which, in use, is associated therewith. The metal members 10-13, inclusive, may to advantage be formed of titanium and in this case a forsterite ceramic having matching expansion characteristics is employed for the insulators -17, inclusive. This ceramic material and a composite body of titanium and this material are more fully described and claimed respectively in Patents No. 2,912,340, dated November 10, 1959, and No. 2,962,136, dated November 29, 1960, both assigned to the assignee of the present application. The parts thus far described are bonded together in stacked relation shown in accordance with methods well understood in the art and may be bonded by the process described in detail and claimed in Beggs Patent No. 2,857,663, dated October 28, 1958, and assigned to the assignee of the present invention. In accordance with the method there described, an eutectic alloy of the titanium members and a bonding shim or washer which may be of copper or nickel, for example, is formed in place by heating the assembly within an evacuated bell jar while the parts are biased together by a weight or spring.

The active electrodes of the device are supported within the envelope provided by the terminals and insulating spacers and electrically connected with the respective terminals. As shown in the drawing the anode 19 is in the form of a cylindrical body of refractory metal such as tungsten. The grid includes a grid washer 20 to which are bonded a plurality of fine and closely spaced grid wires 21, the grid being retained in position against the upper surface of the grid cathode insulator 16 by the inwardly directed flange 22 formed on the grid ring 12. All parts of the grid may be of tungsten, for example. The cathode assembly includes a generally cylindrical cathode cup 23, fitted within and bonded to the inner surface of the cathode terminal 11 and housing a spiral resistance heater element 24 having one terminal 25 bonded to the inner wall of the cathode cup and the other terminal 26 thereof passing through an opening 27 in the cathode heater insulator and bonded to the heater terminal 10. The cathode cup 23 may be formed of a refractory metal such as hafnium and provided with a disklike lid or cathode base 23 to the upper surface of which is applied a coating of the electron emission enhancing material which may be a mix of alkaline earth carbonates usually referred to as a double carbonate coating. The cathode substrate 23 may be any of the known cathode materials such as cathode nickel, tungsten or platinum, for example. The cup 23 is preferably a drawn cup which is vacuum tight so that when bonded to the terminal 11 forms a separate hermetically sealed compartment for the resistance heater element in accordance with the invention described and claimed in my copending application Serial No. 239,114, filed concurrently herewith.

The flexible diaphragm 18 forming one end closure of the envelope may be formed of a thin sheet of molybdenum of platinum, for example, and having a thickness in the order of 1 to 5 mils. This diaphragm is bonded both to the anode terminal 13 and to the ceramic ring 17 which as previously stated provides the dielectric portion of the radial transmission line. The radial dimension of the line may have an electrical length of a little over oneeighth of a wavelength at the operating frequency and usually less than a quarter wavelength. Also, the thickness of the insulator 17 depends on the dielectric constant of the material and in the specific devices described is in the order of 10 to 30 mils.

In accordance wtih an important feature of the present invention, means are provided for adjusting the operating frequency of the device. This may be in terms of an initial adjustment to establish the operating frequency or a continually operable adjustment for varying the frequency of the device. The modification shown is particularly suited for an initial adjustment. The anode and the diaphragm are bonded to an anode stud which may be a generally cylindrical body of copper or other material having good heat transfer characteristics 30 and provided with an outwardly extending flange 31. The cooling of the anode is accomplished by a generally cylindrical finned radiator 32 which is split longitudinally on one side of the center at 33 to permit easy assembly of the radiator on the anode stud. It is clamped in position by means of suitable bolts 34 arranged to draw the split portions of the radiator tightly together. The radial flange 31 is provided with three adjusting screws 35 which threadingly engage the anode terminal 13 to move the anode toward the grid and three additional screws 36 which threadingly engage the outwardly extending flange 31 on the anode stud and abut against the upper surface of the anode terminal 13 to move the anode away from the grid. In order to provide positive stops to limit the movement of the anode and flexible diaphragm 18, anode stud 30 is provided with a section 37 of reduced cross section, the upper and lower surfaces of which provide shoulders for engagement with an inwardly directed flange formed on the anode terminal. In order to facilitate assembly the flange 38 is made as a separate split ring secured to the terminal 13 by suitable screws 39. It will be apparent to those skilled in the art that the adjusting screws 35 may threadingly engage both flange 31 and terminal 13 and provided with thumb wheels if continual adjustment of the device is contemplated. In such a construction the screws 36 may be omitted.

From the foregoing detailed description, it will be apparent that I have provided an electric discharge device having an output cavity resonator directly incorporated in the tube structure and that in the specific form of the illustrated embodiment this structure involves very little complication and makes possible this functional arrangement in a structure similar to the disk seal type of device which has proved so satisfactory for high frequency operation. Also, the structure provides an improved radial output and means for tuning the cavity.

While I have illustrated my invention in connection with a triode type of device, it may be applied to a tetrode type of device without difficulty. In such a case the plate current is not subject to variation in magnitude with variation in the position of the anode as it is with the triode modification.

While I have described and illustrated a particular embodiment of my invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from my invention in its broader aspects and I aim, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electric discharge device comprising alternately arranged metal and insulating members bonded together to provide a hollow evacuated envelope, the metal members providing externally accessible terminals of the device, anode, grid and cathode electrodes within said device in mutually spaced relation supported from and electrically connected to different ones of said metal members, the support for said anode including a flexible metal diaphragm cooperating with said anode, said grid and a metal member of said envelope to provide an anode-grid cavity resonator having a radial output circuit provided by the metal surfaces bounding the insulator interposed in the envelope wall between said anode and said grid.

2. An electric discharge device comprising alternately arnanged metal and insulating members bonded together to provide a hollow evacuated envelope, the metal members providing externally accessible terminals of the device, anode, grid and cathode electrodes within said device in mutually spaced relation supported from and electrically connected to different ones of said metal members, the support for said anode including a flexible metal diaphragm forming a part of the Wall of the evacuated envelope and cooperating with said anode, said grid and a metal member of said envelope to provide an anodegrid cavity resonator having a radial output circuit provided by the metal surfaces bounding the insulator interposed in the envelope wall between said anode and said grid, and means for moving said anode relative to said envelope to tune said cavity.

References Cited by the Examiner UNITED STATES PATENTS 2,396,802 3/1946 Mouromtseff et al. 3155.48 X

2,404,226 7/ 1946 Gurewitsch 3l55 .44 X 2,803,782 8/1957 Dierner 3l539 X 2,805,362 9/1957 Kline 3 l539.6-l 2,923,847 2/1960 Child's et -.al 313-292 X 3,013,180 12/1961 Peters 315-39 GEORGE N. WESTBY, Primary Examiner. 

1. AN ELECTRIC DISCHARGE DEVICE COMPRISING ALTERNATELY ARRANGED METAL AND INSULATING MEMBERS BONDED TOGETHER TO PROVIDE A HOLLOW EVACUATED ENVELOPE, THE METAL MEMBERS PROVIDING EXTERNALLY ACCESSIBLE TERMINALS OF THE DEVICE, ANODE, GRID AND CATHODE ELECTRONS WITHIN SAID DEVICE IN MUTUALLY SPACED RELATION SUPPORTED FROM AND ELECTRICALLY CONNECTED TO DIFFERENT ONES OF SAID METAL MEMBERS, THE SUPPORT FOR SAID ANODE INCLUDING A FLEXIBLE METAL DIAPHRAGM COOPERATING WITH SAID ANODE, SAID GRID AND A METAL MEMBER OF SAID ENVELOPE TO PROVIDE AN ANODE-GRID CAVITY RESONATOR HAVING A RADIAL OUTPUT CIRCUIT PROVIDED BY THE METAL SURFACES BOUNDING THE INSULATOR INTERPOSED IN THE ENVELOPE WALL BETWEEN SAID ANODE SAID GRID. 